Perform ACK completion after the callback to avoid message loss #2906
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Then please check the following list of things we ask for in your pull request:
make test
with your changes locally? (Ranctest -E broker
as broker baseline testing fordevelop
hangs.)Abstract
The current Mosquitto client implementation might lose QoS1 and QoS2 messages if the application crashes during the hand-off callback.
Based on MQTT section 4.4 Message retry delivery, the application (not the MQTT library) takes ownership of the message:
Behavior changes
The current implementation, on receiving a PUB:
With this change, on receiving a PUB:
Notes
Fixes Client PUB completion (PUBACK, PUBREC/PUBCOMP) should be performed after the application callback. #2884